Electric vehicles and electric-hybrid vehicles are gaining in popularity with consumers. The electric motors in these vehicles are typically powered from multiple storage batteries disposed in a battery pack in the vehicle. If the battery needs to be recharged while the vehicle is parked, a wired coupling device is connected to the vehicle, typically by the vehicle operator. However, some operators object to having to ‘plug-in’ their vehicle each time the vehicle is parked.
Wireless or connector less battery chargers have been proposed, see U.S. Pat. No. 5,498,948 issued Mar. 12, 1996 to Bruni et al. and U.S. Pat. No. 8,008,888 issued Aug. 30, 2011 to Oyobe et al. A known wireless battery charger includes a source resonator or charging pad lying on a parking surface under the vehicle being charged, and a corresponding capture resonator mounted underneath the vehicle. Such wireless battery chargers are most efficient when the vehicle is parked such that the source resonator and capture resonator are horizontally (i.e. laterally and longitudinally) aligned. However, as the source resonator and the capture resonator are underneath the vehicle and/or out of the vehicle operator's view, it is difficult for the vehicle operator to judge where to park the vehicle so that the source resonator and the capture resonator are aligned.
Some current wireless charging systems rely on methods to align the capture resonator attached to the undercarriage of a vehicle with its corresponding source resonator using trial and error positioning of the vehicle relative to the source resonator. These methods are time intensive, with poor repeatable results. Other wireless charging systems utilize wheel stops to align the capture resonator on the vehicle with the source resonator. While these systems may provide precise alignment for one particular vehicle configuration, they are unlikely to provide adequate alignment for a wide variety of vehicles wherein the spatial relationship between the wheels and capture resonator differ. Still other wireless charging systems provide a magnetic beacon signal to guide the vehicle to align the capture resonator with the source resonator. Examples of such systems are described in U.S. patent application Ser. No. 13/677,362 and U.S. patent application Ser. No. 13/677,369, both filed Nov. 15, 2012.
The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.